If I lost my AirPod pros third generation at work somebody stole them and I didn’t set up my find my iPhone to my AirPod pros how would I locate my AirPod pros if I have my IMEI and serial number to my AirPods is that possible to locate online

Without having "Find My" enabled, you basically lost any method that Apple provides you to try to locate then. As muguy has mentioned, you either have to go find them or buy yourself a new set ... just don't forget to enable "Find My" before you do.

Even if I am enabled Find My device option to My AirPods pro, unable to locate the device yet.

I have the serial number with me, Product EIMI also available. is there any further solution to track or locate the theft device ???

even apple Care + warranty services also available on my Device. but no benefit With this available service, I am ashamed about the apple Product . Kindly assist and advise to do further needful at the earliest.

No. You can only use FindMy to track your devices. Learn more https://support.apple.com/guide/airpods/locate-your-airpods-dev8e8b93d71/web

No. You can purchase new ones.